1. Field of the Invention
The present invention relates to a curable resin composition, a cured product thereof and a photosemiconductor apparatus useful as a material for optical devices and optical parts, an insulating material for electronic devices and electronical parts, and a coating material, etc.
2. Description of the Related Art
In general, a photosemiconductor apparatus typified by an LED (light-emitting diode) has characteristics that it has low electric power consumption and long lifetime, so that it has been used in a wide range of applications such as backlight for a mobile phone, backlight for liquid crystal television, lighting for automobile, lighting equipments and sign, etc.
In general, light emitting characteristics of a photosemiconductor apparatus is determined by a combination of the photosemiconductor device and light wavelength conversion material (in the following, it is referred to as “phosphor”) to be added and dispersed in the encapsulant thereof, and it is possible to obtain a photosemiconductor apparatus having a color rendering property with various purposes depending on a weight ratio of the phosphor to be mixed. However, for manufacturing such a photosemiconductor apparatus, it was difficult to prepare a light emitting apparatus having stable color rendering property continuously.
In a specific example, it has been manufactured by filling an encapsulant in which a phosphor has been added to a curable resin composition having high transparency into a package substrate having a concave shape to which photosemiconductor devices have been mounted and wire bonded, by using a dispenser with a predetermined amount, and then, curing the same. In this process, the added phosphor has larger specific gravity as compared with that of the curable resin composition, so that the encapsulant is sedimented due to its own weight at the bottom of the filled apparatus with a lapse of time.
The above can be easily understood since the general phosphor is a material having a density of about 4 to 6 g/cm3 and an average particle diameter of 20 μm or less, while the curable resin composition has a density of about 1 g/cm3, so that the phosphor is sedimented during the encapsulating process in the manufacturing process with a lapse of time.
Accordingly, when an encapsulant in which a phosphor has been mixed is to be filled in a package substrate by using a dispenser, a dispersed state of the phosphor is changed at the initial stage of the manufacturing and at the latter stage of the same in a syringe attached to the apparatus, and a phenomenon occurs that at the initial stage of the manufacturing, a phosphor content in the encapsulant is large, while at the latter stage of the manufacturing, a phosphor content in the encapsulant is small. Whether the phosphor content is large or small is directly related to an amount of light to be light-converted, so that the problem occurs that the color rendering property initially designed is fluctuated, and a product having stable characteristics cannot be obtained.
Further, in the encapsulant to which a phosphor has been added, which is dispensed to a package substrate with a concave shape, sedimentation of the phosphor proceeds at the time of waiting curing by heating, so that a phenomenon occurs that in the package substrate at the initial stage of the manufacture, the phosphor is sedimented, but at the latter stage of the manufacture, the phosphor is not sedimented.
Such a concentration difference of the phosphor at the existing positions in the inside of the package substrate is directly related to an amount of light to be light-converted similarly as mentioned above, so that the problem occurs that the color rendering property initially designed is fluctuated, and a product having stable characteristics cannot be obtained.
As an example which can solve the problems, in Patent Document 1, silicone rubber spherical fine particles having an average particle diameter of 0.1 to 100 μm are added to a thermosetting resin composition. However, according to this method, the silicone rubber spherical fine particles themselves, and a surface treatment component, etc., are inferior in heat resistance and light resistance in many cases, so that the problems are remained. Further, in Patent Document 2, it has been proposed a method of preventing from sedimentation of the phosphor by the method that nanoparticles having an average particle diameter of 1 nm or more and 25 nm or less are dispersed in a nano state.
However, these methods which have been proposed as mentioned above each comprise adding a filler to an encapsulant and dispersing therein, so that the problems still remain that the designed color rendering property is fluctuated due to secondary aggregated particles of the filler and the phosphor, and a product having stable characteristics cannot be obtained.
Further, the problems of discoloration of the filler itself and discoloration due to moisture absorption at the interface between the encapsulant and the filler, etc., occur, so that it has been desired to develop a technique which is capable of preventing from sedimentation of the phosphor without using the filler.
That is, it has been desired to develop a curable resin composition for a photosemiconductor apparatus, which causes no change in a dispersed state of the phosphor at the initial stage of the manufacturing and at the latter stage of the same in a syringe of a dispenser or in a package substrate when the encapsulant to which the phosphor has been dispersed is filled in the package substrate, contains the same amount of the phosphor at the initial stage of the manufacturing and at the latter stage of the same, and can maintain stable brightness and color rendering property.